The present invention is directed to a bicycle hub and, more particularly, to a bicycle hub which is specially suited for use in harsh environments under demanding conditions.
A bicycle hub, such as a front wheel hub, must be capable of withstanding static and dynamic loads while permitting the wheels to rotate smoothly and easily. Some bicycles that are subjected to rough and rapid maneuvers, such as mountain bikes, are equipped with shock absorbers in the front fork. Shock absorbers serve to cushion the impact that is transferred from the road surface to the bicycle body via the wheels when the bicycle is traveling, as well as to increase road contact with the wheels, improve steering control, and the like. Hubs in general need to have high rigidity, but front fork hubs that are provided with shock absorbers need even more rigidity because poor rigidity leads to loss of control in steering.
Front wheel hubs that are primarily used in off-road riding are subject to severe wear due to the entry of dirt, sand, and other foreign matter into sliding members. For this reason, front wheel hubs that incorporate sealed bearings equipped with outer rings, inner rings and rolling members are widely known. In conventional hubs, however, dirt, sand, and other foreign matter get caught between the inner ring and the hub axle when changing hubs outdoors because the hub axle is inserted directly into the inner ring of the bearing. The presence of foreign matter leads to wear in the inner ring of the bearing and in the hub axle, thus damaging the precise alignment required in the hub. Consequently, the desired rigidity of the hub is lost, and the service life of the hub is shortened.
Japanese Laid-Open Patent Application 2-155803 discloses a motorcycle rear wheel apparatus which is provided with a center spacer on the outer periphery of an axle shaft for the purpose of preventing dislocation of hub members. The inner ring of the bearings of this motorcycle rear wheel apparatus are not marred by the axle shaft because the axle shaft is supported by the inner ring of the bearings via the center spacer. However, this design allows foreign matter to easily enter the bearings directly from the outside. If this design is used under harsh conditions, such as those to which mountain bikes are subjected, foreign matter will enter the bearings.